95' Rio Grande. 4WD system is not engaging...

[Sine Deviance]

Yeah... I don't know what is going on. When I shift into 4WD and start moving, the 4WD indicator doesn't light up. Ever. I've tried on road and off road. It's also not the bulb for the indicator because I pulled the gauge cluster out and switched the bulb with a new one, still no dice.

So ... where should I start? Specs of the Jeep are in my sig if you need them. Thanks for any help!

 

[Saddle Tramp]

Front axle shift motor vacuum system is probably to blame; it could be the hoses or the motor. This is a common problem with YJs. Try this article in JP-

http://www.jpmagazine.com/techarticles/drivetrain/axletech/154_0904_dana_30_vacume_disconnect/index.html

 

[Sine Deviance]

Okay so yesterday I got up under there and wrenched around a little. I decided to take off the shift fork housing. First bolt I tried to break loose actually did break So that's the head off one bolt. I took the other three bolts out successfully and I couldn't get that bastid to budge. I guess the dirt and small amounts of rust under there are holding it on tight. I even tapped the housing with a hammer a bunch of times and I tried to pry/tap it off with a chisel... got a little axle grease leakage but it still wouldn't budge.

Do you think this could indicate some other problem (like a broken/stuck shift fork?) Because I checked the vacuum lines and they LOOK good... can't say anything about the vacuum motor down there, haven't been able to test it since I can't get the damn housing loose. Any ideas?

 

[Bounty__Hunter]

Pull the vacuum lines from the shift motor and have somebody shift from 2wd to 4wd while the jeep is running. Feel each line for strong vacuum, it should shift between the two lines as 2wd and 4wd are selected. If it checks out, it's in the axle disconnect mounted to the axle.

If you got gear oil leakage, you're almost there. Try tapping a screwdriver between the disconnect housing and the axle housing.

Once off, make sure the shift fork moves freely by hand.

You can make the shift collar permanently engaged by sliding the collar over both axleshafts and installing the disconnect onto the axle upside down. This way the fork holds the collar in the engaged position.

 

[Sine Deviance]

Pull the vacuum lines from the shift motor and have somebody shift from 2wd to 4wd while the jeep is running. Feel each line for strong vacuum, it should shift between the two lines as 2wd and 4wd are selected. If it checks out, it's in the axle disconnect mounted to the axle.

If you got gear oil leakage, you're almost there. Try tapping a screwdriver between the disconnect housing and the axle housing.

Once off, make sure the shift fork moves freely by hand.

Will do! Thanks BH!

You can make the shift collar permanently engaged by sliding the collar over both axleshafts and installing the disconnect onto the axle upside down. This way the fork holds the collar in the engaged position.

That's an awesome idea that would save me about $100 on OEM replacement or $225 on the manual pull-cable kit. Will this cause any mechanical problems in my front diff down the road if it's always engaged? Will both front wheels always want to turn at the same rate? Also, if I did this, would the Jeep be in permanent 4WD or would I still have to shift into 4Lo/4Hi?

 

[Bounty__Hunter]

Will this cause any mechanical problems in my front diff down the road if it's always engaged? Will both front wheels always want to turn at the same rate? Also, if I did this, would the Jeep be in permanent 4WD or would I still have to shift into 4Lo/4Hi?

If you have the stock open front differential, you will not notice it engaged on the road as long as the front driveshaft is properly balanced.

You will still control 2wd/4wd operation with the transfer case lever, the only thing the disconnect on the front axle does is lock two axleshafts together to make one.

The disconnect only really serves to keep the front tires from turning the front driveshaft while in 2wd, reducing the amount of rotating parts on the road. Later Wranglers and Cherokees did away with the disconnect and spin the driveshaft all the time.

 

[Sine Deviance]

If you have the stock open front differential, you will not notice it engaged on the road as long as the front driveshaft is properly balanced.

You will still control 2wd/4wd operation with the transfer case lever, the only thing the disconnect on the front axle does is lock two axleshafts together to make one.

The disconnect only really serves to keep the front tires from turning the front driveshaft while in 2wd, reducing the amount of rotating parts on the road. Later Wranglers and Cherokees did away with the disconnect and spin the driveshaft all the time.

Ahh. Thanks. I'll definitely consider this option.